Simple enough, but pretty explicit in his directions. He needs venom from the scorpashi, and hide from some kodo. The fine print says both are from specific creatures: the venom's got to come from any of the scorpashi, and the hide's got to come from an aged kodo, not the dying or ancient ones.

The Scorpashi are the scorpions found everywhere in Desolace. The venom drops less than half the time, so you'll be killing a lot of scorpions to complete this.

The Aged Kodo Hides are dropped with pretty much every aged kodo slain.
The aged kodo travel in herds, mostly along the trails (who do you think made the trails) along the south and west, usually ending up near the Kodo Graveyard.